Optical microscopy shows that the storage protein of corn endosperm is deposited within the cells as two distinct components, globular bodies and an amorphous matrix in which the granules are embedded. Bates et al. (Cereal Chem. 58:138, 1981) reported that in Tripsacum dactyloides (2n=36), starch grains and protein bodies were only one-tenth as large as those of maize, and ranged from 1.3 to 1.8 um and from 0.05 to 0.12 um respectively. In accordance with the results of Bates et al., Tripsacum dactyloides (2n=36) has no visible protein bodies at the light microscope level. The purpose of the present paper is to make known the experimental results which we have obtained in the study of Tripsacum dactyloides (2n=72) endosperm structure. Mature kernels were thin sectioned, destarched with alpha-amylase, and endosperm tissue studied using optical microscopy at 700 x magnification. The procedure employed for observation of protein bodies was the same as the one described by Wolf and Khoo (Stain Tech. 45:277, 1970). Protein body size and starch grain size were measured in the third or fourth cell layer below the aleurone layer, because the protein bodies decreased in size from the aleurone layer inward.
Figure 1 shows that Tripsacum has visible protein bodies. We found that Tripsacum protein bodies ranged from 0.4 to 0.8 um in diameter (average 0.6 um) and that starch grains ranged from 3.4 to 4.5 um in diameter (average 4.0 um). The results presented here indicate that starch grains and protein bodies of Tripsacum dactyloides (2n=72) were only one-half as large as those of maize. Our results are significantly different from those reported by Bates et al., therefore it is probable that the ploidy level in Tripsacum dactyloides conditions different endosperm structures in the same species.
Jorge Luis Magoja and Luis Maximo Bertoia
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